Question

我正在做这个应用程序，用户需要传递两个Int值，当按下按钮并且没有输入任何值时应用程序崩溃。我该如何解决这个问题？我认为它与可选值有关。

这是我的代码：

class ViewController: UIViewController {
    @IBOutlet var age_1: UITextField!
    @IBOutlet var age_2: UITextField!
    @IBOutlet var emoji_button: UIButton!
    @IBOutlet var date_textField: UILabel!

    let colorProvider = BackgroundColorProvider()

    @IBAction func button_pressed(_ sender: AnyObject) {
        // Compare 2 given ages(int) and tell if people can date.
        let me_age =  Int(age_1.text!)!
        let other_age = Int(age_2.text!)!
        let me_age_min  = (me_age / 2) + 7
        let me_age_max = (me_age - 7) * 2

        if me_age == 0 || other_age == 0 {
            date_textField.text = "Enter ages then touch the heart"
        }else if me_age > 18 && other_age < 18{
            date_textField.text = "Don't date an under-age."
        }// Case 2: Person is older and cant´date younger:
        else if me_age < 18 && other_age > 18{
            date_textField.text = "You are under age."
        }else if me_age == other_age{
            date_textField.text = "You definetly should date."
        }else if other_age < me_age_min {
            print (me_age_min)
            date_textField.text = "To young 4 U"
        } // Case 3: Person is young and can't date older:
        else if other_age > me_age_max {
            print ((me_age - 7) * 2 )
            date_textField.text = "To old 4 U"
        } // Case 4: Both people are the same age:
           else{
            date_textField.text = "Yes, you can date. "
        }

Answer 1

我会重写这两行：

let me_age =  Int(age_1.text!)!
let other_age = Int(age_2.text!)!

使用：

guard let me_age = Int(age_1.text ?? "") else {
    date_textField.text = "Enter valid number into age1" //Replace this line to any code you prefer
    return
}
guard let other_age = Int(age_2.text ?? "") else {
    date_textField.text = "Enter valid number into age2" //As well as the line above
    return
}

如果age_1.text为nil，则age_1.text!会崩溃。
如果age_1.text!不是有效整数，则Int(age_1.text!)!会崩溃。
如果age_2.text为nil，则age_2.text!会崩溃。
如果age_2.text!不是有效整数，则Int(age_2.text!)!会崩溃。

因此，人们将!称为崩溃我运算符，如果您不想让应用崩溃，最好避免使用它。

（语义上age_1或age_2可以是nil，但如果您正确连接@IBOutlet这不是问题。）

Answer 2

如果Int(someStr)会得到nil，无论字符串是""还是其他字符串，所以你不能nil!，你可以判断textField.text是否int在获得value let me_age = Int(age_1.text!)! let other_age = Int(age_2.text!)!之前，1}}为空。

替换两行：

    var me_age:Int
    if let age1 = Int(age_1.text!) {


        me_age = age1

    }else {

        // there alert to ask user type in age_1
        print("ask user to type in current age_1 ")
        return
    }

    var other_age:Int
    if let age2 = Int(age_2.text!) {


        other_age = age2

    }else {

        // there alert to ask user type in age_1
        print("ask user to type in current age_2")
        return
    }

要：

age

首先，如果您想在textField中输入textField，则应将keyboard的{{1}}类型设置为Number Pad。

应用程序崩溃，因为UITextField中的空Int值

2 个答案: